Measuring instrument



Dec. 14 1926. 7 1,610,227

c. T. ALLCUTT MEASURING I NSTRUMENT Filed July 7, 1920 WITNESSES: INVENTOR W! 01165161" TAJ/wjj va- 4 BY I v Patented: 14 ,1

CHEQTER -fA L fi -t at: enema s m YivAiiiA," i erates Tb wE Tmel ou'sn d an;anzrn mcmnmne ooiiirnivirin. coRroRATioN or. PENNSYL- .YVIAN'IA.

f Mar uerit restate-ram.-

a Application med m 7, 1920. ser ia1'1v 94,454."

invention 1 relates to measuring sys tems and particularly to means" for, and methods of, measuring the phase-sequence components of an electrical quantity.

One? object of 7 my invention isto provide- I a devieefor indicating theiposit'iveand negative phaser'sequence component'of the volt it age ona polyphase electric circuit,

Another object'of my invention is't'o provide: a measuring device, of i the above f1nd1= para'tus; H I v i My lnventio'n 1s m thenature of an 1minexpensive to construct from Standard approvement upon that disclosed in U. S. Let- 7 ters Patent, No. 1,535,593, issued April28, V 1925, upon an application filed'by 0. L:

F ortescue, L. W. Chubb and J. Slepian, disclosing means whereby an unbalanced poly: phase quantitymay be separated into a plurality of. balanced quantities.

My inventioninvolves th broad principle of the 7 above mentioned application but greatly simplifies the device whereby the de- SllGCl results may be obtained.

In practicingmy invention, I .provide a 'polyphase induction motor which is so connected to a polyphase circuit asto be operated on single phase only. When the motor operates, it generates equal voltages in its various polyphase windings and the difference between the line voltage and the generate'd voltage is a measure of the positive tween the idle phase winding of the motor or negative phase-sequence component, de-

" pending upon the direction of rotation of the motor. In order todetermine this difi'erence in voltage, a voltmeter is connected beand the remaining phase of the circuit.

Figure 1 of the accompanying drawlngs is a diagrammatic view of-the measuring.

device embodying'my invention, and

Fig. 2 is a diagram illustrating the relation of the various electrical quantities involved in the invention. I I A three-phase circuit 1 comprises conductors 2, 3 and 4 across which is impressed an unbalanced voltage or which is traversed by such an unbalanced load that the voltage thereaoross is unbalancedr It is desired to determine the various phase-sequence com ponents of the voltagewhich may be called a -measure of the unbalanceof the circuit tremet v te se A polyphese m to having three;star-connected windings 6,7 and '8 and rotor '9, is so connected to the motor and induces e ual voltages inith e g wvinding's '6, 7 and .8. flhe "d-ifiererice in pic;- cated character, that shall be simple and;

martial-between the point '11 dtt h winding 6 (and the conductor 2 a measure of the negative phase-sequence coinponent or the v9 'i's'op'eratec'l as the rotor-nit ajsingle-phase unbalanced voltage impressed on the circuit 1. If the rotor 9 is rotated in the opposite direction, the meter 10 will indicate the positive phase-sequence component of the voltage impressed across-the circuit 1. Opposite rotat on of the motor may be -obtained by-br nging'thermotor up to synchronous speed manually in the other direction or the same result may be obtained by temporarily 1 reversing the connection of the windings- 7 and8 to the conductors 3 and 1 until the motor has come up to speed and then reconnecting the motor as shown.

For approximate results, an ordinary induction motor having uniform windings 6,.

7 and 8 in order that the voltagesinduced 7 and 8 may be used but, if very accurate re- 7 sults are desired, the winding 6 must be of a lessnumber of turns than the windings therein maybe exactly balanced when the I motor is running unloaded.

In Fig. 2 of the'drawings, the linesj12,

Band 14 representthe voltages impressed- -on the-circuit 1. It will be seen that these voltages areunbalanced. The voltages rep- 7 resented by the lines 1 1, 15 and 16 are the voltages generated in the windings 6, 7 and .8 by the rotation of the rotor r9 and the line 17 represents the diifere'ncebetween the generated voltage l and the voltages impressed ,onthe circuit 1. In other words, the indication of the meter 10 is a measure of the, line by the lines 12, 1 3 and 14L.

unbalanced three-phase voltages indicated ioo length of the line 17 is proportional to the negative phase-sequence"component'of the My inventlon 1s not limited tothe specific structures illustrated as it may be variously modified Without departing from, the spirit and scope of the invention, as set forth in the appended claims.

I'claim as my invention '1. The combination With a polyphase e1ec-' tric circuit and a polyphase induction motor,

of means for: connecting one inding toconductors' or one phase .of the circuit; and

means comprising a voltmeter for connecting another Winding of the motor to another phase conductor oi' -the circuitr I 2. The combination With-a polyphase electric; circuit anda polyphase star-connected motor, of means for so connecting two'windings thereor across one phase of the circuit as to d ive the motor from the circuit, and an electroresponsive device connected between the open; phase oft-he motor and the other phase of the circuit.

3, A measuring device for a polyphase electr c circuit comprising a three-phase .1111:

duction motor, means for connecting two of the" phase windings thereof across tvvo condoctors ofe the'circuit to causethemotor to operate on a single phase and means for ina min the difference a 'potential betiveen "the remaining phase Winding and the other the circuit. e V V e 5. A measuring device Ifor a' 'polyphase electriczocircnit comprising a poiyphase motor, means for connecting the motor. to

the circuit to effect operation of the motor,

and means connected between one of the phase w ndings of the motor and the circuit for indicating one 7 phase-sequence '1 component of the-voltage onftheicircuit. e

- In testimony whereof, I have hereunto subscribed my 1920. j"

C ESTER "r. ALLoUT'r;

name. this 24cth day of .Jnne,

Jhase-se uence comoonent of the ,volta 'e of i V V e a V V 

